[PATCH v2] clk: Add driver for the si544 clock generator chip
From: Mike Looijmans
Date: Thu Mar 15 2018 - 07:50:27 EST
This patch adds the driver and devicetree documentation for the
Silicon Labs SI544 clock generator chip. This is an I2C controlled
oscillator capable of generating clock signals ranging from 200kHz
to 1500MHz.
Signed-off-by: Mike Looijmans <mike.looijmans@xxxxxxxx>
---
v2: Add u64 cast to ls_div_bits calculation loop
When ls_div_bits is non-zero, the hs_div must always be even
.../devicetree/bindings/clock/silabs,si544.txt | 25 ++
drivers/clk/Kconfig | 10 +
drivers/clk/Makefile | 1 +
drivers/clk/clk-si544.c | 422 +++++++++++++++++++++
4 files changed, 458 insertions(+)
create mode 100644 Documentation/devicetree/bindings/clock/silabs,si544.txt
create mode 100644 drivers/clk/clk-si544.c
diff --git a/Documentation/devicetree/bindings/clock/silabs,si544.txt b/Documentation/devicetree/bindings/clock/silabs,si544.txt
new file mode 100644
index 0000000..eec1787
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/silabs,si544.txt
@@ -0,0 +1,25 @@
+Binding for Silicon Labs 544 programmable I2C clock generator.
+
+Reference
+This binding uses the common clock binding[1]. Details about the device can be
+found in the datasheet[2].
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+[2] Si544 datasheet
+ https://www.silabs.com/documents/public/data-sheets/si544-datasheet.pdf
+
+Required properties:
+ - compatible: One of "silabs,si514a", "silabs,si514b" "silabs,si514c" according
+ to the speed grade of the chip.
+ - reg: I2C device address.
+ - #clock-cells: From common clock bindings: Shall be 0.
+
+Optional properties:
+ - clock-output-names: From common clock bindings. Recommended to be "si544".
+
+Example:
+ si544: clock-generator@55 {
+ reg = <0x55>;
+ #clock-cells = <0>;
+ compatible = "silabs,si544b";
+ };
diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index 98ce9fc..5c7dc8e 100644
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig
@@ -91,6 +91,16 @@ config COMMON_CLK_SI514
This driver supports the Silicon Labs 514 programmable clock
generator.
+config COMMON_CLK_SI544
+ tristate "Clock driver for SiLabs 544 devices"
+ depends on I2C
+ depends on OF
+ select REGMAP_I2C
+ help
+ ---help---
+ This driver supports the Silicon Labs 544 programmable clock
+ generator.
+
config COMMON_CLK_SI570
tristate "Clock driver for SiLabs 570 and compatible devices"
depends on I2C
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 71ec41e..bde614a 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -44,6 +44,7 @@ obj-$(CONFIG_COMMON_CLK_S2MPS11) += clk-s2mps11.o
obj-$(CONFIG_COMMON_CLK_SCPI) += clk-scpi.o
obj-$(CONFIG_COMMON_CLK_SI5351) += clk-si5351.o
obj-$(CONFIG_COMMON_CLK_SI514) += clk-si514.o
+obj-$(CONFIG_COMMON_CLK_SI544) += clk-si544.o
obj-$(CONFIG_COMMON_CLK_SI570) += clk-si570.o
obj-$(CONFIG_ARCH_STM32) += clk-stm32f4.o
obj-$(CONFIG_ARCH_STM32) += clk-stm32h7.o
diff --git a/drivers/clk/clk-si544.c b/drivers/clk/clk-si544.c
new file mode 100644
index 0000000..a392acf
--- /dev/null
+++ b/drivers/clk/clk-si544.c
@@ -0,0 +1,422 @@
+/*
+ * Driver for Silicon Labs Si544 Programmable Oscillator
+ *
+ * Copyright (C) 2018 Topic Embedded Products
+ *
+ * Author: Mike Looijmans <mike.looijmans@xxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+/* I2C registers (decimal as in datasheet) */
+#define SI544_REG_CONTROL 7
+#define SI544_REG_OE_STATE 17
+#define SI544_REG_HS_DIV 23
+#define SI544_REG_LS_HS_DIV 24
+#define SI544_REG_FBDIV0 26
+#define SI544_REG_FBDIV8 27
+#define SI544_REG_FBDIV16 28
+#define SI544_REG_FBDIV24 29
+#define SI544_REG_FBDIV32 30
+#define SI544_REG_FBDIV40 31
+#define SI544_REG_FCAL_OVR 69
+#define SI544_REG_ADPLL_DELTA_M0 231
+#define SI544_REG_ADPLL_DELTA_M8 232
+#define SI544_REG_ADPLL_DELTA_M16 233
+#define SI544_REG_PAGE_SELECT 255
+
+/* Register values */
+#define SI544_CONTROL_RESET BIT(7)
+#define SI544_CONTROL_MS_ICAL2 BIT(3)
+
+#define SI544_OE_STATE_ODC_OE BIT(0)
+
+/* Max freq depends on speed grade */
+#define SI544_MIN_FREQ 200000U
+
+/* Si544 Internal oscilator runs at 55.05 MHz */
+#define FXO 55050000U
+
+/* VCO range is 10.8 .. 12.1 GHz, max depends on speed grade */
+#define FVCO_MIN 10800000000ULL
+
+#define HS_DIV_MAX 2046
+#define HS_DIV_MAX_ODD 33
+
+enum si544_speed_grade {
+ si544a,
+ si544b,
+ si544c,
+};
+
+struct clk_si544 {
+ struct clk_hw hw;
+ struct regmap *regmap;
+ struct i2c_client *i2c_client;
+ enum si544_speed_grade speed_grade;
+};
+#define to_clk_si544(_hw) container_of(_hw, struct clk_si544, hw)
+
+/* Multiplier/divider settings */
+struct clk_si544_muldiv {
+ u32 fb_div_frac; /* Integer part of feedback divider (32 bits) */
+ u16 fb_div_int; /* Fractional part of feedback divider (11 bits) */
+ u16 hs_div; /* 1st divider, 5..2046, must be even when >33 */
+ u8 ls_div_bits; /* 2nd divider, as 2^x, range 0..5 */
+};
+
+/* Enables or disables the output driver */
+static int si544_enable_output(struct clk_si544 *data, bool enable)
+{
+ return regmap_update_bits(data->regmap, SI544_REG_OE_STATE,
+ SI544_OE_STATE_ODC_OE, enable ? SI544_OE_STATE_ODC_OE : 0);
+}
+
+/* Retrieve clock multiplier and dividers from hardware */
+static int si544_get_muldiv(struct clk_si544 *data,
+ struct clk_si544_muldiv *settings)
+{
+ int err;
+ u8 reg[6];
+
+ err = regmap_bulk_read(data->regmap, SI544_REG_HS_DIV, reg, 2);
+ if (err)
+ return err;
+
+ settings->ls_div_bits = (reg[1] >> 4) & 0x07;
+ settings->hs_div = (reg[1] & 0x07) << 8 | reg[0];
+
+ err = regmap_bulk_read(data->regmap, SI544_REG_FBDIV0, reg, 6);
+ if (err)
+ return err;
+
+ settings->fb_div_int = reg[4] | (reg[5] & 0x07) << 8;
+ settings->fb_div_frac = reg[0] | reg[1] << 8 | reg[2] << 16 |
+ reg[3] << 24;
+ return 0;
+}
+
+static int si544_set_muldiv(struct clk_si544 *data,
+ struct clk_si544_muldiv *settings)
+{
+ int err;
+ u8 reg[6];
+
+ reg[0] = settings->hs_div;
+ reg[1] = settings->hs_div >> 8 | settings->ls_div_bits << 4;
+
+ err = regmap_bulk_write(data->regmap, SI544_REG_HS_DIV, reg, 2);
+ if (err < 0)
+ return err;
+
+ reg[0] = settings->fb_div_frac;
+ reg[1] = settings->fb_div_frac >> 8;
+ reg[2] = settings->fb_div_frac >> 16;
+ reg[3] = settings->fb_div_frac >> 24;
+ reg[4] = settings->fb_div_int;
+ reg[5] = settings->fb_div_int >> 8;
+
+ /*
+ * Writing to SI544_REG_FBDIV40 triggers the clock change, so that
+ * must be written last
+ */
+ return regmap_bulk_write(data->regmap, SI544_REG_FBDIV0, reg, 6);
+}
+
+static bool is_valid_frequency(const struct clk_si544 *data,
+ unsigned long frequency)
+{
+ unsigned long max_freq;
+
+ if (frequency < SI544_MIN_FREQ)
+ return false;
+
+ switch (data->speed_grade) {
+ case si544a:
+ max_freq = 1500000000;
+ break;
+ case si544b:
+ max_freq = 800000000;
+ break;
+ case si544c:
+ max_freq = 350000000;
+ break;
+ default:
+ return false;
+ }
+
+ if (frequency > max_freq)
+ return false;
+
+ return true;
+}
+
+/* Calculate divider settings for a given frequency */
+static int si544_calc_muldiv(struct clk_si544_muldiv *settings,
+ unsigned long frequency)
+{
+ u64 vco;
+ u32 ls_freq;
+ u32 tmp;
+ u8 res;
+
+ /* Determine the minimum value of LS_DIV and resulting target freq. */
+ ls_freq = frequency;
+ settings->ls_div_bits = 0;
+
+ if (frequency >= (FVCO_MIN / HS_DIV_MAX))
+ settings->ls_div_bits = 0;
+ else {
+ res = 1;
+ tmp = 2 * HS_DIV_MAX;
+ while (tmp <= (HS_DIV_MAX * 32)) {
+ if (((u64)frequency * tmp) >= FVCO_MIN)
+ break;
+ ++res;
+ tmp <<= 1;
+ }
+ settings->ls_div_bits = res;
+ ls_freq = frequency << res;
+ }
+
+ /* Determine minimum HS_DIV by rounding up */
+ vco = FVCO_MIN + ls_freq - 1;
+ do_div(vco, ls_freq);
+ settings->hs_div = vco;
+ /* round up to even number when required */
+ if ((settings->hs_div & 1) &&
+ ((settings->hs_div > HS_DIV_MAX_ODD) || settings->ls_div_bits))
+ ++settings->hs_div;
+ /* Calculate VCO frequency (in 10..12GHz range) */
+ vco = (u64)ls_freq * settings->hs_div;
+ /* Calculate the integer part of the feedback divider */
+ tmp = do_div(vco, FXO);
+ settings->fb_div_int = vco;
+ /* And the fractional bits using the remainder */
+ vco = (u64)tmp << 32;
+ do_div(vco, FXO);
+ settings->fb_div_frac = vco;
+
+ return 0;
+}
+
+/* Calculate resulting frequency given the register settings */
+static unsigned long si544_calc_rate(struct clk_si544_muldiv *settings)
+{
+ u32 d = settings->hs_div * BIT(settings->ls_div_bits);
+ u64 vco;
+
+ /* Calculate VCO while preventing overflow */
+ vco = (u64)settings->fb_div_int * FXO;
+ vco += (((u64)settings->fb_div_frac * FXO) + (FXO / 2)) >> 32;
+
+ do_div(vco, d);
+
+ return vco;
+}
+
+static unsigned long si544_recalc_rate(struct clk_hw *hw,
+ unsigned long parent_rate)
+{
+ struct clk_si544 *data = to_clk_si544(hw);
+ struct clk_si544_muldiv settings;
+ int err;
+
+ err = si544_get_muldiv(data, &settings);
+ if (err) {
+ dev_err(&data->i2c_client->dev, "unable to retrieve settings\n");
+ return 0;
+ }
+
+ return si544_calc_rate(&settings);
+}
+
+static long si544_round_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long *parent_rate)
+{
+ struct clk_si544 *data = to_clk_si544(hw);
+ struct clk_si544_muldiv settings;
+ int err;
+
+ if (!rate)
+ return 0;
+
+ if (!is_valid_frequency(data, rate))
+ return -EINVAL;
+
+ err = si544_calc_muldiv(&settings, rate);
+ if (err)
+ return err;
+
+ return si544_calc_rate(&settings);
+}
+
+/*
+ * Update output frequency for "big" frequency changes
+ */
+static int si544_set_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long parent_rate)
+{
+ struct clk_si544 *data = to_clk_si544(hw);
+ struct clk_si544_muldiv settings;
+ int err;
+
+ if (!is_valid_frequency(data, rate))
+ return -EINVAL;
+
+ err = si544_calc_muldiv(&settings, rate);
+ if (err)
+ return err;
+
+ si544_enable_output(data, false);
+
+ /* Allow FCAL for this frequency update */
+ err = regmap_write(data->regmap, SI544_REG_FCAL_OVR, 0);
+ if (err < 0)
+ return err;
+
+
+ err = si544_set_muldiv(data, &settings);
+ if (err < 0)
+ return err; /* Undefined state now, best to leave disabled */
+
+ /* Trigger calibration */
+ err = regmap_write(data->regmap, SI544_REG_CONTROL,
+ SI544_CONTROL_MS_ICAL2);
+ if (err < 0)
+ return err;
+
+ /* Applying a new frequency can take up to 10ms */
+ usleep_range(10000, 12000);
+
+ si544_enable_output(data, true);
+
+ return err;
+}
+
+static const struct clk_ops si544_clk_ops = {
+ .recalc_rate = si544_recalc_rate,
+ .round_rate = si544_round_rate,
+ .set_rate = si544_set_rate,
+};
+
+static bool si544_regmap_is_volatile(struct device *dev, unsigned int reg)
+{
+ switch (reg) {
+ case SI544_REG_CONTROL:
+ case SI544_REG_FCAL_OVR:
+ return true;
+ default:
+ return false;
+ }
+}
+
+static const struct regmap_config si544_regmap_config = {
+ .reg_bits = 8,
+ .val_bits = 8,
+ .cache_type = REGCACHE_RBTREE,
+ .max_register = SI544_REG_PAGE_SELECT,
+ .volatile_reg = si544_regmap_is_volatile,
+};
+
+static int si544_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ struct clk_si544 *data;
+ struct clk_init_data init;
+ int err;
+
+ data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ init.ops = &si544_clk_ops;
+ init.flags = 0;
+ init.num_parents = 0;
+ data->hw.init = &init;
+ data->i2c_client = client;
+ data->speed_grade = id->driver_data;
+
+ if (of_property_read_string(client->dev.of_node, "clock-output-names",
+ &init.name))
+ init.name = client->dev.of_node->name;
+
+ data->regmap = devm_regmap_init_i2c(client, &si544_regmap_config);
+ if (IS_ERR(data->regmap)) {
+ dev_err(&client->dev, "failed to allocate register map\n");
+ return PTR_ERR(data->regmap);
+ }
+
+ i2c_set_clientdata(client, data);
+
+ /* Select page 0, just to be sure, there appear to be no more */
+ err = regmap_write(data->regmap, SI544_REG_PAGE_SELECT, 0);
+ if (err < 0)
+ return err;
+
+ err = devm_clk_hw_register(&client->dev, &data->hw);
+ if (err) {
+ dev_err(&client->dev, "clock registration failed\n");
+ return err;
+ }
+ err = of_clk_add_hw_provider(client->dev.of_node, of_clk_hw_simple_get,
+ &data->hw);
+ if (err) {
+ dev_err(&client->dev, "unable to add clk provider\n");
+ return err;
+ }
+
+ return 0;
+}
+
+static int si544_remove(struct i2c_client *client)
+{
+ of_clk_del_provider(client->dev.of_node);
+ return 0;
+}
+
+static const struct i2c_device_id si544_id[] = {
+ { "si544a", si544a },
+ { "si544b", si544b },
+ { "si544c", si544c },
+ { }
+};
+MODULE_DEVICE_TABLE(i2c, si544_id);
+
+static const struct of_device_id clk_si544_of_match[] = {
+ { .compatible = "silabs,si544a" },
+ { .compatible = "silabs,si544b" },
+ { .compatible = "silabs,si544c" },
+ { },
+};
+MODULE_DEVICE_TABLE(of, clk_si544_of_match);
+
+static struct i2c_driver si544_driver = {
+ .driver = {
+ .name = "si544",
+ .of_match_table = clk_si544_of_match,
+ },
+ .probe = si544_probe,
+ .remove = si544_remove,
+ .id_table = si544_id,
+};
+module_i2c_driver(si544_driver);
+
+MODULE_AUTHOR("Mike Looijmans <mike.looijmans@xxxxxxxx>");
+MODULE_DESCRIPTION("Si544 driver");
+MODULE_LICENSE("GPL");
--
1.9.1